V-grooved sheave



June 12, 1923.

D. L. LINDQUlST V-GROOVED SHEAVE Filed July 12 1919 Patented June 12, 1923.

UNH'TED STATES LdSdAZS PATENT @FIFHCE.

DAVID L. LINDQUIS'I', OF YONKERS, NEW YORK, ASSIGNOR TO OTIS ELEVATOR COM- PANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

V-GROOVED SHEAVE.

Application filed July 12, 1919.

To all whom it may concern:

Be it known that I, DAVID L. LIND UIsT, a subject of the King of Sweden, residing in Yonkers, in the county of Westchester and State of New York, have invented a new and useful Improvement in V-Grooved Sheaves, of which the following is a specification.

My invention involves a new and useful grooved sheave for use in elevators, and relates more particularly to a wedge form of groove in the driving sheave of a traction elevator, in which there is but a single half turn or wrap of the hoisting rope in the groove in the sheave.

The objects of the invention are to provide a Wedge form of groove in which the friction between the sheave and rope will remain as nearly constant as practicable in the use of the sheave and rope and throughout the wear between them, in order to obtain as far as practicable constant tractive efiect between the sheave and rope, and, also, to reduce as nearly as practicable the wear between the parts, and, further, any other advantage which may prove to be due to the improved form of groove in the sheave.

In a traction elevator, the grooved driving sheave is used to carry and drive the hoisting rope of the car and counterweight, which are hung from the ends of the rope. It is customary in the art of traction elevators to form the sides of the groove straight and inclined at an angle to each other to constitute a wedge shaped groove, and to use round wire ropes, in the angle of which groove the rope lays and is wedged and pinched between opposite points of contact with the inclined sides of thegrooves by the weight of the rope, the car and counterweight; the more acute the angle the greater will be the friction between the sheave and rope, and the larger the ability of the sheave to move or drive the rope. It is familiar experience in the operation of the elevator to find that the rope wears or I. cuts its way through the material of the inclined sides of the groove in virtually a straight line substantially parallel with the plane through the center line of the rope until it has formed a circular groove for itself at the bottom, which originally was an Serial No. 310,410.

inclined groove and upon the bottom of which circular groove the rope rests. In such case, the friction is comparatively considerably reduced, and the pinching effect on the rope between it and the sheave is greatly reduced, and the ability of the sheave to drive the rope is lessened with the loss of the pinching effect. It has been the practice in the art of traction elevators to pass the hoisting rope around the grooved driving sheave in at least two half wraps or turns, it being found that such a form of wrapping is usually sufficient to obtain all the tractive effect between the sheave and rope that is necessary in all conditions of duty load in the car with the rope resting upon the bottom of a circular groove. But now it is more and more becoming the practice in the traction elevator art merely to take a half-wrap or turn of the hoisting rope over the grooved sheave, and in which case, it is believed to be the better practice not only to have a wedge-shaped groove in the sheave, between the inclined sides of which the rogue shall be wedged or pinched, but that even t ough the rope wear away the sides of the wedge in straight lines substantially parallel to the plane through the center line of the rope, the pinching effect between the groove and rope shall be substantially retained and maintained.

In the drawing, Figure 1 is a view in cross section of the conventional Wedge-shaped form of groove with the outline of the circumference of a wire rope, of several strands, indicated as laying in the groove.

Figure 2 is a view in cross-section of my improved form of groove with the outline of the circumference of a wire rope, indicated as laying in the wedge of the groove.

Figure 3 is a view in cross-section of my improved preferred form of groove, with the outline in full line of the circumference of .a wire rope, indicated as laying in the wedge of the groove.

Figure 4 is a view in cross-section of a portion of a grooved driving sheave for a traction elevator, with my improved preferred form of groove, as shown in Figure 3.

Figure 5 is a view in cross-section of another form of my improved groove, in which a short portion of the sides of the upper wedge of V-shaped groove,

wedge is curved, with the outline of a rope indicated as laying in the curved portion 0 the sides of the roove.

Similar numera s refer to similar parts throughout the several views.

Referring to Figure 1 or the drawing, a section of a driving sheave, S, for a traction elevator is shown, with the ordinar G, therein, wit the outline, in full lines, of the circumference of a wire rope, R, comprised of strands 1', with the rope pinched in the groove, between the points of contact a and b. When the rope is new, the contacts between the sides of the groove and the rope are virtually merely points of contact. In that position, the rope, by the weight of the car and counterweight, is held as in a Wedge, and, therefore, the friction is accordingly considerable, which prevents the slipping of the rope in the operation of the elevator.

When wear takes place (assuming the sheave only to wear), the position of the rope will be, say as indicated in the circular dotted line, C, in Figure 1. It will be seen that the rope has worn straight through the inclined sides of the wedgeshaped groove, and that instead of the rope being pinched between the two inclined sides of the wedge-shaped groove as was originally the case, it is supported by the arcs ale and fg, constituting practically a circular groove in which the rope rests. As a consequence, the friction obtained by'the pinching of the rope when the groove was new and the rope rested on the contact points a and b is substantially lost, and accordingly the friction very much diminished, and slipping between the sheave and rope will occur at a much lesser load in the car than when the rope was in its original position, because the sum of all the various pressures over the arcs do and fg is very much less than was the total pressure on the points a and b.

My improved groove, which will be referred to herein, as the progressive wedgeshaped groove, has ior its object to lessen, minimize or avoid the loss of friction when the sides of the wedge-shaped groove wear or in other words virtually to retain and maintain the inching of the rope in the groove notwit standing the wear of the sides of the groove.

Referring to Figure 2, when the rope is in the position, 1, as indicated by the circular full line, the rope is in the wedge between the contact points, a and b, which is the same as if the rope were held in a wedge as in Figure 1. From the points a and d, the sides of the groove fall straight down in lines, 2, parallel with each other. The straight lines, 3, which the sides of the rope will describe in wearing away the sides of the groove, will be substantially parallel I and as a consequence,

with the lines, 2, of the groove. The result f will be that if the wear of the sides of the sheave occur so that the rope assumes the position, 4, indicated by the circular dotted line, it will be supported on the arcs, hi and jk, and the pinching of the rope is still retained, and maintained without perceptible diminution of friction between the rope and sheave, because the sum of the various pressures over the arcs hi and ii: is substantially equal to the total preure on the points aand b.

While above it has been assumed that the sides of the groove only wear, it is a matter of fact that the rope also wears and becomes smaller in diameter as the wear increases. To compensate for the rope wear and still retain the pinching of the rope, it is evident that the lower part of the groove, as shown in Figure 2, cannot have its sides- 02' and dis, arallel with the plane through the center line of the rope, but that those sides should taper slightly towards the middle of the groove, beginning, say, at

the points 0 and d. This modification is shown in Figure 3, wherein each side "of the groove is formed of two straight lines, 5 and 6, inclined at diiferent angles, the wedge extending from the to of the groove to point-s, o and d, and anot er wedge with a smaller angle extending downward beginning at those points. When new, the rope is held in the position 1 between the contact points a and b, as indicated in the circular full line in Figure 3. When wear has taken place, the position of'the rope will be as indicated by the dotted circular line, which is shown with a considerably reduced diameter to indicate wear of the rope itself. Had the wedge been of a single angle as in Figure 1, the supporting arcs, when the sides of the roove have been worn away, would have on the arcs, de and fg, which would constitute practically merely a circular groove in which the rope would lay, as shown in Figure 1. It will be seen that by changing the slope or angle of the sides of the wedge below the points 0 and d, the supporting arcs for the rope in the position indicated by the dotted circular line when wear has occurred will only be the arcs hi and 970, which are placed at a very'much more acute angle than the ares ale and fg, Figure 1, the pinching effect of the wedge on the rope has been virtually retained and maintained, notwithstanding both the rope and the sides of the groove have become worn. The friction, therefore, is more nearly constant in the improved form of groove than is possible with a straight wedge as in Figure 1.

It is found that my improved forms of grooves shown in'Figures 2, 3 and 4, can be readily made with the usual effort expended in machine shop practice, without resorting meaeee to such a painstaking degree of care in doing the work of shaping the groove, and an expenditure of time and labor thereon which might be found to be unnecessary in the successful cooperative use of the pulley and rope in the operation of an elevator in maintaining the friction between the pulley and, rope more nearly constant than is maintainable in the case of a mere straight wedge shown in Figure 1; but where it is desirable to establish in the beginning the required tractive relation between the pulley and rope, and thereafter to maintain that condition as nearly constant as may be throughout the period of use and wear of the pulley and rope and yet avoid the sticking of the rope in the groove in its movement in leaving the'groove, I have devised a form of groove, shown in Figure 5, in which that portion of the bottom of the groove upon which the rope would rest, were the bottom of the groove made circular to conform to the shape of the rope, is cut away; the width between the sides of the groove of the portion cut away being determined by the diameter of the rope and the desired traction, so that when the rope is first laid in the wedge it will rest upon what are practically short supporting arcs, Zm and no, Figure 5, as indicated in the circular full line delineating the rope, in which position the required tractive and pinching effect upon the rope is obtained in the groove, and without the rope sticking in its movement in leaving the groove in the operation of the pulley and rope. The width of the portion to be taken out of the bottom of the groove, or stated in other words, the width between the ends of the arcs, is ascertained by calculating the traction required. For example, in Figure 5, the width of the portion taken out of the bottom of the groove between the ends of the arcs is .indicated as being between the radial lines from the axis of the arcs to the ends of the arcs. The angle between these radii may be referred to or called the angle determining the width of the portion to be taken out of the bottom of the groove or stated in other words, the angle determining the ends of the arcs or stated in other words, the extent that the arcs should be in order to obtain the traction required for a given elevator. The Figure 5 is not drawn to exact scale, but it is close enough to scale to illustrate the principle of the invention. For instance, the angle between said radii is shown as approximately 105. When wear has taken place, and the rope has changed its initial position relatively to the depth of the groove, say, for example, to the position indicated in the dotted circular line, Figure 5, it will be perceived that the rope rests upon the small arcs, hi and jlc, which are practically similar to the arcs, Zm and no,

and defined by an angle of approximately 105, therefore the same or substantially the same tractive effect of the wedge is maintained throughout the cooperative use of the pulley ind rope as obtained in the initial position of the rope in the wedge; the figure also shows a vertical line through the axis of the arcs and lines extended from the lower ends of the arcs and tangent to the arcs all meeting the vertical line at a common point. The angle defines the angle for the sides of the undercut portion of the groove, and hence, stated in other words, the proper angularity of the sides for the undercut portion in order to maintain the traction constant during the wear of the groove and rope; and yet without any sticking of the rope in the wedge in its movement in leaving the pulley, and as a consequence, the frictional effect between the rope and wedge will be retained and maintained virtually constant, notwithstanding the rope and the groove may have become worn in their cooperative use, and the rope changed its position relatively to the depth of the groove. The tractive condition of the rope and pulley, therefore, is maintained more nearly constant in my improved form of groove than is possible with the conventional form of groove with straight sides, shown in Figure 1. It is understood of course that the traction required is different between elevators having different speeds, weights of car and counterweight and live load, though the diameter of the ropes may be one and the same, and therefore that the Widths of the portion to be undercut between the arcs or shelves which support the ropes or, in brief, the angles of undercut, will be different and the angles between the sides for the undercut portion of the groove will also be different in the respective elevators. For examples, for an elevator having, say, six ropes, and a given speed, weights of car, counterweight and load and traction required, let it be assumed that the proper width of undercut calls for an angle of 105 for the undercut portion and an angularity according thereto for the sides of the undercut portion of the groove as delineated in Figure 5; whereas, in another elevator, having say four ropes, and a given different speed, etc. and traction required, it will be found that the suitable angle for the undercut portion will be different from an angle of 105. say, for illustration, that the angle of required undercut is 90 and, therefore, the angle according thereto for the sides of the under-cut portion of the groove will also be different from the angle of the sides of the undercut portion of the groove for the elevator in which an angle of 105 for the undercut was assumed. In view of said differences among elevators, the drawing in the application might have contained additional figures showing grooves of different angles of undercut and sides of the undercut portion as further illustrations of the application of the principle of my invention of maintaining the traction required constant throughout the use of the groove and rope from their original condition to their worn condition; for instances, the additional illustrations might have shown grooves with angles of undercut portion ranging say, from 30 to 45 to 60 to 90, adapted to elevators having say, four ropes with a certain speed, weights of car and counterweight and load and required traction relation, and from angles of 90 to 100 adapted to elevators having say, five ropes, and other certain speeds, weights of car, etc., and /or even through other angles to an angle of say, 110 for the undercut portion adapted to elevators having still other speeds, etc. and eight ropes, though in the example, last mentioned, it will be found that the rope may stick more or less in the groove in leaving it, which, of course, is objectionable and should be avoided. In commercial practice it will be found that a range of angles for the undercut portion of from 90 to 105 and angles according thereto for the sides of the undercut portion of the groove, as explained above, will take care of the generality of traction elevators. I It is thought that the description of the groove and illustrations in the figures of the drawing are sufficient to disclose the principle of my invention and its application to produce or obtain grooves with different widths of undercut portions, defined by different angles, according to the traction required for a given elevator, and different sides of the undercut portion of the grooves, defined by different angles according to the widths or angles of the undercut portion.

What I claim is:

1. The herein described sheaves for hoisting ropes of traction elevators, having wedge shaped grooves and circular arcs for supporting the ropes with the required traction for the elevators and an undercut portion between the ends of the arcs, the width of the undercut being defined by angles of from 30 to 110 measured between straight lines drawn from said ends of the arcs toward the axis of the pulley and the sides of the undercut portion of the groove defined by straight lines drawn from said ends of the arcs intersecting each other at a point in a vertical line extended from the axis of the arcs and which said point is also the point of intersection of straight lines drawn tangent to the arcs.

2. The herein describedsheaves for the hoisting ropes of traction elevators, having wedge shaped grooves and circular arcs for supporting the ropes with the required traction for the elevators and an undercut portion between the ends of thearcs, the width of said portion being defined by angles of from 90 to 105 measured between straight lines drawn from the ends of the arcs at said ends of the arcs toward the axis of the pulley, and the sides of the undercut portion of the groove defined by straight lines drawn from said ends of the arcs intersecting each other at a point in a vertical line extended from the axis of the arcs and which said point is also the point of intersection of straight lines drawn tangent to the arcs.

3. A new article, the herein described sheave having an annularly grooved rim for single wrap hoisting cables of traction elevators, the bottom of the grooves being wedge-shaped and adapted to support the cables, the Width of the wedge-shaped grooves being determined by the diameter of the cables, the desired tractive effect, and release of the cables from 'the wedge-shaped grooves in their movement without sticking, the joints between the walls of the top and bottom of the grooves constituting practically short supporting surfaces for the cables in which position the desired tractive and pinching effect without sticking of the cables in the wedge-shaped grooves in their movement in leaving the grooves is obtained, and virtually retained and maintained during the life of the cables in the wedge-shaped grooves.

4. As a new article of manufacture, the herein described grooved traction sheave for the hoisting cables of traction elevators having a groove each side of which is constituted of an upper and lower. straight surface and a circular are surface joining together in the sides the straight surfaces, the straight surfaces making an angle between the sides of the groove, and the bottom of the groove cut away or undercut in straight lines produced from the straight line of the lower straight side sufficiently deep to prevent the cable from reaching the bottom of the groove.

5. As a new article of manufacture, the herein described grooved sheave for the hoisting cables of traction elevators, having grooves, the cross-section of the bottom of which is round, and of the diameterdetermined by the diameter of the ropes which are to be used therein, the bottom of the grooves being undercut wedge-shaped substantially in the middle of their width, whereby two round supporting arcs or seats for the ropes are produced, the sides of the undercut portion converging towards each other at an angle such that the maximum traction without sticking of the ropes in the grooves in their movement of release therefrom will obtain throug t the life of the cables.

6. As a new article Ianufacture, the herein described grooved sheave for the hoisting cables of traction elevators, having grooves, the cross-section of the bottom of which is round and of the diameter determined by the diameter of the ropes which are to be used therein, the bottom of the grooves being undercut wedge-shaped substantially in the middle of their width, whereby two round supporting arcs or seats for the ropes are produced, the sides of the undercut portion converging towards each other at an angle such that the required traction without sticking of the ropes in the grooves in their movement of release therefrom will obtain throughout the life of the cables.

In testimony whereof, I have signed my name to this specification in the presence of a subscribing witness.

DAVID L. LINDQUIST.

Witness FREDERICK W. MIDGLEY. 

